1. Field of the Invention
The present invention relates to a method and an apparatus for communication between coordinator-based wireless networks connected through a backbone network, and more particularly, to a method and an apparatus for communication between multiple coordinator-based wireless networks connected through a wired backbone network by means of a wired/wireless relay device.
2. Description of the Related Art
With the development of communication and network technologies, recent network environments have been in the transition from wired network environments using wired media such as coaxial cables or optical cables to wireless network environments using radio signals over various frequency bands. Accordingly, computing devices (hereinafter referred to as “wireless network devices”) have been developed, which include wireless network interface modules, have mobility, and perform specific functions by processing various information. In addition, wireless network technologies have appeared, which allow such wireless network devices to efficiently communicate with each other.
Generally, a wireless network may be classified into the following two types of networks.
First, as shown in FIG. 1, there is a type of wireless network including an access point, which is called an infrastructure mode wireless network.
Further, as shown in FIG. 2, there is another type of wireless network including no access point, which is called an ad-hoc mode wireless network.
In the infrastructure mode wireless network, an access point performs a relay function of transmitting data in order to connect a wireless network to a wired network or to allow wireless network devices to be communicated with each other in a wireless network. Accordingly, all data must pass through the access point.
Next, the ad-hoc mode wireless network is formed only when a network is required randomly. In the ad-hoc mode wireless network, wireless network devices in a single wireless network directly exchange data with each other without passing through a relay device such as the access point.
Such a network may be classified into two types of networks. In a first network type, a wireless network device designated randomly among wireless network devices belonging to a single wireless network functions as a coordinator which assigns a time period (hereinafter referred to as “a channel time”), during which data can be transmitted to the other wireless network devices. Further, the other wireless network devices can transmit data only for a determined channel time. In a second network type, there is no wireless network device functioning as a coordinator, and all wireless network devices can transmit data whenever they want to transmit data.
Herein, in the former case, that is, in the network type (hereinafter referred to as “a coordinator-based wireless network”) in which a wireless network device functioning as a coordinator exists, an independent single wireless network is formed on the basis of the coordinator. Further, when a plurality of coordinator-based wireless networks exist in a predetermined area, each of the coordinator-based wireless networks has unique identification information in order to be distinguished from other coordinator-based wireless networks.
Accordingly, wireless network devices belonging to a specific coordinator-based wireless network can exchange data with other wireless network devices in the same coordinator-based wireless network for a channel time, which is determined by a coordinator, but cannot communicate with wireless network devices belonging to other coordinator-based wireless networks.
For instance, as shown in FIG. 3, in a home network system including three coordinator-based wireless networks 310 to 330, it is assumed that the wireless network 310 is constructed in a first-floor living room, the wireless network 320 is constructed in a second-floor study room, and the wireless network 330 is constructed in a first-floor bedroom.
Herein, a user in the second-floor study room cannot see a movie stored in a media server 315 in the first-floor living room by means of a portable dynamic image player 325 in the second-floor study room because there is no method for enabling communication between the wireless network 310 and the wireless network 320. Accordingly, the user must come down to the first-floor living room to see the movie.
Such a problem is caused because of a limitation in a transmission distance of radio waves, an absence of information on other coordinator-based wireless networks and an assignment problem of a channel time, etc.
Accordingly, it is necessary to construct a new network topology for exchanging data between wireless network devices belonging to different coordinator-based wireless networks.